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Obesity

Obesity is a dimension of body image based on a society’s consideration of acceptable body size and, as such, is the focus of anthropological, sociological, and psychological study (de Garine and Pollock 1995). However, most of the research on obesity in Western societies has focused on medical issues ranging from genetic etiology to therapeutic interventions. Overfatness or obesity is a major health problem in countries that are affluent and is increasing in prevalence among the socioeconomic elite of those that are modernizing. An estimated 90 million Americans—one-third of the population—are substantially above their range of desirable body weight; in some other populations more than half of their members fit into this category.

Of course, some fat or adipose tissue is essential for life and serves a number of functions. It provides metabolic fuel; thermal insulation; a reservoir for vita-mins, hormones, and other chemicals; and protection for the viscera and dermal constituents, such as blood vessels, nerves, and glands (Beller 1977). However, an excessive accumulation of fat is associated with an increased risk for diabetes, hypertension, cardiovascular and musculoskeletal problems, and in general, a reduced life expectancy. Moreover, in many societies, fatness elicits a psychosocial stigma.

Definitions and Diagnosis

Body weight is the most widely used anthropometric indicator of nutritional reserves, and weight relative to height is an acceptable measure of body size for growth monitoring and for most epidemiological surveys. Over-weight and obesity, though often used synonymously, are not the same. S. Abraham and co-workers (1983) clearly made the distinction in analyzing data from the first U.S. National Health and Nutrition Examination (NHANES) survey. Overweight was defined as an excess in body weight relative to a range of weights for height. In this report, individuals over the 85th percentile of weight for height standards are considered overweight. Obesity was defined as an excess of body fat based on the sum of the triceps (upper arm) skin-fold and subscapular (back) skinfold. Skinfold measurements using calipers that pinch a fold of skin and sub-cutaneous fat at specific sites (for example, waist, abdomen, thighs, upper arm, and back) are used in equations to estimate body fat stores and are compared with reference percentile tables (Himes 1991).

Many recent studies have used the Body Mass Index (BMI), which is the weight in kilograms divided by height in meters squared, to categorize body size. This index was devised by the Belgian mathematician Adolphe Quetelet (1796-1874) and is also referred to as the Quetelet index. (The Ponderal Index,which is the quotient of the height in inches divided by the cube root of the weight in pounds, has been similarly used.) Overweight is defined as a BMI above 27.3 for women and 27.8 for men. These BMIs represent approximately 124 percent of desirable weight for men and 120 percent of desirable weight for women, defined as the midpoint of the range of weight for a medium-size skeletal frame from the 1983 Metropolitan Insurance Company Height and Weight Tables. The World Health Organization uses a similar range of BMIs: below 20 (lean), 20 to 25 (acceptable), 25 to 29.9 (moderately overweight), 30 to 39.9 (severely obese), and greater than 40 (morbidly obese). Epidemiological studies frequently use a BMI of 30 as the delimiter for obesity for both sexes.

Other anthropometric measurements have been used as alternatives to body weight in assessment of obesity. Body girth measurements or circumferences at specific anatomical locations have a high correlation with body mass. A commonly used measure is the circumference of the upper arm. This measurement, in conjunction with the triceps skinfold, has been used to compare the fat and lean components of the arm and thus to provide a measurement of energy and protein stores. More sophisticated, expensive, and time-consuming techniques assess the lean and fat components of the body. These techniques have included densitometry, magnetic resonance imaging (MRI), basic X rays, computerized tomography (CAT) scans, ultrasound, bioelectrical impedance, total body water, and body potassium levels (Lukaski 1987).

Skinfolds, circumferences, and imaging techniques assess the regional distribution of fat deposits. A central distribution of fat is referred to as an apple shape. A lower torso distribution of fat on the hips is referred to as a pear shape. The apple shape, often measured as a high waist-to-hip ratio of circumferences, is associated with internal deposits of abdominal fat and increased risk for coronary artery disease and adult onset diabetes. By contrast, the pear shape is not associated with increased disease risk (Bouchard and Johnston 1988).

Epidemiology

Current estimates of the prevalence of obesity indicate that it has reached epidemic proportions in some populations. The most widely cited statistics on weight are those from NHANES III and are based on a random sample of the U.S. population between 1988 and 1991 in which 31 percent of males and 35 percent of females ages 20 to 74 years were considered overweight. Table IV.E.7.2 presents the percentages of adults defined as obese with BMIs • 30. More alarming are the recent estimates of the percent overweight and obese done by the Institute of Medicine of the National Academy of Science (1995).Viewed in light of BMIs that are 25 or greater, 59 percent of American males and 49 percent of females are overweight or obese. Two percent of males and 4 percent of females are considered morbidly obese with BMIs over 40. A 5-foot 4-inch woman with a BMI of 40 weighs 230 pounds.

A survey of Micronesian Islanders indicates that 85 percent of males and 93 percent of females are over-weight, whereas among native Hawaiians, a Polynesian group, 85 percent of males and 62 percent of females are overweight. Obesity is also prevalent in a number of native North American groups. A survey of Seminoles and Pimas has revealed that more than 50 percent of the adults are obese, whereas among the Canadian Cree and Ojibwa more than 90 percent of females and between 45 and 54 percent of males were so categorized. Among other ethnic groups within the United States there also are high levels of adult obesity: In Texas, fully 66 percent of male Mexican-Americans and 60 percent of females are obese, as were almost 50 percent of female African-Americans and 31 percent of males nationwide. Table IV.E.7.1 and Table IV.E.7.2 present the proportion of obese or over-weight adults in a number of countries.

Obesity can begin in early life. Eleven percent of U.S. children (ages 6 to 11 years), 13 percent of adolescent males (ages 10 to 17), and 9 percent of adolescent females are overweight. Outside of the United States, M. Gurney and J. Gorstein (1988), who surveyed the preschool populations of 34 countries, found ranges of obesity from 1 to 11 percent. By way of a few examples, in Jordan and Tahiti 2 percent of the preschoolers were obese, in the United Kingdom 3 percent, in Canada 6 percent, and in Jamaica the figure was 10 percent. There are no comparable multinational studies for school-age children.

Obesity in childhood and adolescence is a good predictor of obesity in adulthood. In one study, a third of the obese adults examined were already over-weight or obese at 7 years of age, and two-thirds were overweight or obese by age 14. Studies in the United States and Britain found that between 40 and 74 percent of obese 11- to 14-year-old youngsters became obese young adults.

Secular Trends in Overweight

Since 1960, surveys in the United States have tracked changes in the proportion of those overweight and obese in the population. In general, adult average weight and the proportion of individuals who are overweight have grown larger. Overweight prevalence for adults increased 8 percent between the recording periods of NHANES II (1976-80) and NHANES III (1988-91).The mean BMI jumped from 25.3 to 26.3 and the mean body weight increased by 3.6 kg. The proportion of overweight children and adolescents, in particular, has been augmented, although a countertrend can be seen among the older (over 70 years) segment of the population. Thus for women 60 to 74 years of age, there was a decrease in the percent overweight from 45.6 percent to 41.3 percent. However, among African-American females, corresponding figures for the younger cohort (50 to 59 years) showed an increase from 35 to 52 percent overweight. By contrast, African-American males age 60 to more than 80 years had the lowest percent of overweight individuals in comparison with white and Hispanic Americans. It is notable that during the two decades from 1960 to 1980, no consistent secular trends were found for whites or blacks ages 12 to 17 years and 18 to 34 years. However, this changed significantly with the NHANES III data, which revealed increasing obesity in both of these groups.

Based on self-reports in a Harris Poll, 74 percent of Americans ages 28 and older stated in 1996 that they were overweight. This was an increase from 71 percent in 1995, 69 percent in 1994, and 59 percent in 1986. In the United Kingdom during the decade 1980 to 1990, the percentage of adult males classified as overweight grew from 39 to 48 percent and those who were obese from 6 percent to 8 percent. The proportion of women classified as overweight increased from 32 percent to 40 percent and obese from 8 percent to 13 percent. Overweight percentages were highest for males and females 50 to 64 years of age.

Gender

Childbearing and menopause are associated with weight gain, obesity, and an increasing waist-to-hip ratio. Maternal body fat is gained during pregnancy in response to the hormonal milieu, with a third of women gaining more than 5 kilograms of adipose tissue. In the United States, the mean net weight gain with each childbearing cycle is 1 kilogram above that normally gained with aging. Americans put on approximately 20 pounds from age 25 to 55. Lactation mobilizes fat, but selectively from the femoral region, and, therefore, there is still an increase in the waist-to-hip ratio. Menopause has also been reported to increase the waist-to-hip ratio and add an average 20 percent body fat mass, compared to the premenopausal state. Both subcutaneous and internal visceral abdominal fat increase in postmenopausal women.

Obesity is approximately twice as prevalent among women as men in the United States, although this disparity is the most striking in certain populations, such as African-Americans, Mexican-Americans, Puerto Ricans, and Western Samoans. By contrast, Hawaiians, Nauruans, Native Americans, Alaskan natives, and Mexican-Americans have the highest obesity prevalence among males. Obesity is only slightly more prevalent among black, Puerto Rican, and Cuban-American men than among non-Hispanic white men. Asian-Americans (of Chinese, Japanese, Filipino, and Indochinese origin) have a lower obesity prevalence than other minority groups in the United States, although this may be changing. Some groups, such as the California Japanese, have recently developed moderately high BMIs.

Brown and M. Konner (1987) have noted that females appear to become obese with modernization. They suggested that the sex ratio of obesity is a marker for a population on a trajectory of economic development and westernization. That is, an excess of female versus male obesity is more likely to be observed in poorer populations in the developing world and less so in affluent Western populations. The data are generally consistent with this interpretation.

Brown’s (1991) cross-cultural survey using the Human Relation Area File data found that 81 percent of societies for which there was sufficient data rated “plumpness” or being “filled out” as an attribute of beauty in females. This was particularly true of fat deposits on the hips and legs. Bigness for women in some groups is a sign of power, beauty, and maternity. Indeed, anthropologists have described the practices of populations in Polynesia (Pollock 1995) and West Africa (Brink 1995), where young women are secluded for a year or more in “fattening huts” prior to marriage. Such plumpness is not only considered desirable in a woman but also reflects positively on the socioeconomic status of her family and its ability to feed a daughter without having to rely on her labor.

Modernization

The construct of modernization encompasses a wide variety of lifestyle changes, including physical activity patterns, diet, and psychosocial stress. Many “diseases of civilization” (Trowell and Burkitt 1981) have been associated with westernization or modernization.

For example, the Pimas of Arizona have the highest rate of diabetes of any known population—a condition that is accompanied by a high prevalence of obesity among individuals of all ages. However, this is not the case with a small group of Pima whose ancestors migrated to Mexico some 700 to 1,000 years ago and who live today in a remote, mountainous location with a traditional lifestyle that is in marked contrast to the Arizona Pima. These Mexican Pima are lighter in weight and shorter and have lower BMIs, plasma cholesterol levels, and rates of diabetes. Consequently, it would seem that much of the problem with the Arizona Pima lies in lifestyle. Suggestive as well was a study conducted by K. O’Dea (1984), who took a group of diabetic Australian Aborigines away from an urban lifestyle to live as hunters and gatherers for seven weeks in northwestern Australia. The subjects lost an average of 8 kilograms and experienced improved carbohydrate metabolism.

In another study, the situation was reversed, whereby 13 Tarahumaras living a traditional lifestyle in northern Mexico were fed a diet typical of affluent societies for five weeks. On average, these subjects gained 3.8 kilograms (or 7 percent of their initial body weight) and had dramatic increases in plasma lipids and lipoprotein levels. Clearly, such investigations indicate that aspects of modern lifestyle can significantly contribute to obesity as well as other deleterious metabolic changes. They point to the benefits of a diet low in animal fat and high in complex carbohydrates, as well as the importance of high levels of physical activity (McMurphy et al. 1991).

In addition, migration studies have shown that populations moving from traditional to westernized environments experience large increases in body weight, along with rising rates of diabetes and other metabolic changes (Bindon and Baker 1985; Bindon 1995).

Geography

Derek Roberts’s study (1953) of the geography and climate of 220 societies revealed that height and weight ratios are related to mean annual temperatures and that people are fatter the farther away they live from the equator. In other words, populations are fattest where summers are the coldest and leanest where summers are the hottest (Beller 1977). Put another way, if height is held constant, heavier people are found in the world’s colder climates. Roberts hypothesized that cold stimulates the adrenal glands which, in turn, increase fat deposits.

In the United States, obesity is most common in the Northeast and Midwest, and rates are significantly higher in metropolitan regions than in rural areas. However, cutting across geographic distinctions are ethnic group concentrations and socioeconomic classes. In modernizing countries, the more affluent segments of populations exhibit a higher prevalence of obesity regardless of rural or urban location. But in industrialized countries, the lower socioeconomic classes have the higher prevalence, and in addition, immigrant populations show increases in body weight compared to their sedentary counterparts or populations of origin. Finally, within a country, migration from rural to urban areas also leads to obesity.

Lifestyle Factors

Physical Activity

Physical inactivity has been related to increases in body weight and to obesity in both children and adults. Research by William Dietz and S. L. Gortmaker (1985) has demonstrated a linear relationship between the number of hours of television watching and body weight among Americans. Moreover, cross-sectional studies indicate that there is a negative relationship between energy expended for physical activity and body fat content. However, these associations do not prove that low levels of physical activity promote high levels of body fat because the association can also mean that individuals with existing high levels of body fat are rendered unable to exercise vigorously or for extended durations.

Both aerobic exercise and resistance training result in decreases in body fat by increasing energy expenditure during the actual period of exercise and subsequent periods of rest. Thus, exercise can promote a negative energy balance provided that there is not compensatory energy intake for those calories expended during and after exercise. Exercise has been found to be moderately successful in promoting and maintaining weight loss, and in some studies, weight loss was sustained with moderate exercise after the cessation of dieting.

Diet

Suzuki and N. Hosoya (1988) have succinctly modeled the relationship between obesity in adulthood and dietary changes, by arguing that modernized diets and food habits tend to accelerate the storage of body fat, regardless of the amount of energy that is ingested. Involved are (1) decreased carbohydrate and increased fat proportions in daily energy intake; (2) gorging just before resting; (3) increase of simultaneous intake of fats and sugars; (4) increased consumption of cereals in refined forms, such as flour, rather than unrefined, unprocessed grains; (5) increased consumption of soft, digestible foods rather than hard and more difficult to digest (for example, fibrous) foods; and (6) increased consumption of alcohol.

Although the primary focus has been on caloric intake, data also indicate that the composition of the diet is important in terms of metabolic rate, energy storage, and the production of obesity. Both the amount and the composition of food influence bodyweight regulation. In a clinical study by T. Horton and colleagues (1995), carbohydrate overfeeding produced progressive increases in oxidation and total energy expenditure, resulting in 75 to 80 percent of excess energy being stored. Fat overfeeding had a minimal effect on oxidation and total energy expenditure, leading to storage of 90 to 95 percent of excess energy. Excess dietary fat led to a greater fat accumulation than did excess dietary carbohydrates. Other investigations have demonstrated that individuals with a family history of obesity are more likely to suffer the obesity-promoting effects of high-fat diets than individuals without such a family history (Bouchard and Bray 1996).

Epidemiologic data from both the United States and Great Britain have shown that sugar intake is inversely related to obesity prevalence but that BMI and the percent of calories from fat are positively correlated. Indeed, a number of studies indicate that it is dietary fat, rather than sugar intake, that promotes obesity. However, a high-carbohydrate intake may cause hyperinsulinemia that, in turn, promotes fat storage. Excess intake of any macronutrient can contribute to weight gain, especially when associated with low energy expenditure.

The nutritional epidemiological transitions that promote obesity are, in part, fueled by multinational food corporations, which have introduced calorically dense foods that are advertised widely. The U.S. Department of Agriculture estimates that in the United States alone, the food and restaurant industry spends approximately 36 billion dollars annually on advertising, and some campaigns for single items (for example, a new soft drink or a new hamburger) exceeded 50 million dollars in 1996 and 1997. The trend in the United States is to increase the size of fast-food items (for example, “supersize,” or “giant size”), which are generally high in fat, carbohydrates, sodium, and calories to begin with. The larger portions tend to be eaten as quickly and completely as the regular ones. Thus, McDonald’s “supersize” serving of fries, which contains 540 calories, represents a 20 percent increase in calories over their “regular” serving. A “king size” candy bar may be as much as 80 percent larger than the regular size bar, and a large popcorn in a movie theater is 50 percent bigger than a medium size. In the United States, a mean of 3,700 kilocalories are available each day for every man, woman, and child, representing a third more than the recommended dietary allowance for men and twice that for adult women.

The explosion of “light” and “low fat” and “fat free” foods has led consumers to believe that these items are also calorie reduced or even calorie free, although their caloric content may be equal (or nearly so) to the nonspecialized product. (One venerable exception is the diet soft drink, and the new calorie-free fat substitutes now entering the market may constitute others.) Salad bars, also popular in the United States, can be equally deceptive. Consumers put high-calorie salad dressings on low-calorie salads to the extent that the caloric content of the salad exceeds that of a meal containing animal protein and fat. American women 19 to 50 years of age get more fat from salad dressings than from any other food (Hurley and Collins 1997).

Obesity is promoted not only by the consumption of fat but also by the overconsumption of carbohydrates and protein. Americans, in particular, are consuming too many of these macronutrients while maintaining or insufficiently reducing their intake of fats. Data from NHANES I (1970s) and NHANES II (1976-80) indicated that Americans only reduced their fat intake from 42 percent to 38 percent of calories—still far above the recommended fat intake of 30 percent of total daily calories (Bray 1993b).

Smoking

Smokers weigh consistently less than nonsmokers, and when individuals stop smoking they generally gain weight. Ex-smokers reach body weights similar to those of age- and sex-matched nonsmokers, although gross obesity appears to be more frequent in ex-smokers than in those who have never smoked. The increases in body weight of ex-smokers stem from a number of causes, including increased food consumption and decreased metabolic rate. In one study, it was found that young adults who smoked 24 cigarettes per day had a 200 kilocalorie greater daily expenditure of energy than when not smoking, and this increased energy expenditure was independent of energy intake and physical activity (Hofstetter et al. 1986). Another study revealed that middle-age and older male smokers had higher waist-to-hip ratios than nonsmokers, after controlling for BMI, dietary and alcohol intake, and activity levels (Troisi et al. 1991).

Socioeconomic Factors

Many studies have demonstrated a striking inverse relationship between socioeconomic status and the prevalence of obesity, particularly among women in developed countries. This relationship is true regardless of whether socioeconomic status (SES) is based on family income, educational level, or occupation. Fully 30 percent of women of lower SES in the United States are obese compared with less than 5 percent of those of the upper status groups. Some investigations have demonstrated that upwardly mobile women are less obese than women who remain in a low SES. The prevalence of obesity for men in lower SES is 32 percent compared with 16 percent among upper-class men.

Obesity is a socioeconomic disability in Western cultures. In general, the theory is that socioeconomic status influences obesity by education, income, and occupation, causing variations in behavior that change energy consumption and expenditure. However, obesity influences socioeconomic status by the stigmatization and discrimination it elicits, which, in turn, limits access to higher SES roles. There are ample data showing discrimination against obese individuals in terms of access to education, hiring for a variety of occupations, salary, and advancement (Allon 1982; Cassell 1995).

In a pioneering study, J. Sobal and A. J. Stunkard (1989) looked at the relationship between socioeconomic status and obesity in both developed and developing societies. They found that there was an inverse relationship between SES and obesity in industrialized societies, even stronger for women than for men, but a direct relationship in developing societies. The data pertaining to children are less clear. For boys in industrialized societies, the relationship between SES and obesity was either inverse or absent, but in developing countries it was clearly direct. For girls in industrialized countries, the relationship was inverse, as it was for women, whereas no relationship was found in developing countries.

Income is related to obesity mostly through access to resources. Individuals and families with higher incomes have more options in terms of access to food and food choices, although actual caloric intake may not vary by income. Occupation is related to obesity primarily through lifestyle factors in terms of energy expenditure on the job and during leisure activities. And finally, educational levels have been related to the prevalence of obesity, as lower educational levels are associated with lower income.

History of Obesity

Anthropological constructions have indicated a hunter-gatherer lifestyle during most of human history that was marked by much physical activity to secure adequate food, interspersed seasonally with decreased food intake. This variation selected genetically for individuals who were able to store energy as fat to carry them through lean times. Both contemporary foraging populations and those engaged in the incipient domestication of plants and animals show seasonal changes in weight that reflect variations in the availability of foods.

Studies of traditional hunting and gathering populations report no obesity. In contrast, many examinations of traditional societies undergoing processes of modernization that include production of generally high-carbohydrate food crops demonstrate a rapid increase in the prevalence of obesity. In fact, H. C. Trowell and D. P. Burkitt (1981) have noted that obesity in modernizing societies is the first “disease of civilization” to appear. The rapidity with which obesity becomes a health problem in the modernization process highlights the critical role of behavioral factors in its causation, as well as the evolutionary genetic propensities that were adaptive for traditional, calorically expensive lifeways.

Given the rarity of obesity in preindustrial societies, it is not surprising that there is a lack of ethnomedical terms for the obese state (Brown 1991). In fact, thinness has often been seen as a symptom of starvation or as a sign of disease, whereas plumpness has been viewed as a marker of health. For example, the Tiv of Nigeria distinguish between the very positive category of “too big” and the unpleasant condition of “to grow too fat.” In some societies, for women in particular, fatness has been and remains a symbol of maternity and nurturing. The concepts that fat babies and children are healthy and that food is a symbol of love and nurture are nearly universal (Brown and Konner 1987). Moreover, from an evolutionary perspective, there are many biological advantages to the maintenance of energy stores as fat. These include an ability to survive longer during a fast, a greater ability to fight infectious diseases, fewer gastrointestinal tract problems, less anemia, healthier and higher birth-weight babies, and earlier age of menarche (Cassidy 1991).

The ethnographic data concerning body preferences in males is relatively weak, although it does suggest a preference for a more muscular physique, moderately tall stature, and general largeness.Traditionally, big, but not necessarily obese, men have been seen as successful. However, historical trends show variations in positive and negative associations with obesity.

Historical Medical Concepts

George Bray (1992) has outlined the scientific and medical history of ideas concerning obesity. In the Hippocratic texts, obesity was associated with infertility in women, a laxity of muscle, a red complexion, and sudden death. To lose weight meant strenuous physical activity before consuming meals prepared with sesame seasoning and fat because these satiated appetite. Dieters were to eat just once a day, take no baths, sleep on a hard bed, and walk naked as long as possible. Galen (130-215), who followed in the Hippocratic tradition, identified types of obesity and prescribed bulky foods with low nutrient content, baths before eating, and vigorous exercise.

The first monographs in which obesity was the primary subject were published in the seventeenth century. A mechanistic model of the body was popularly invoked, although there were other theories about fatness based on fermentation and putrefaction as the basis for an iatrochemical model.

The medical history of the eighteenth century was dominated by Hermann Boerhaave (1688-1738), who has been called the “most successful clinician and medical teacher of the century” (Ackerknecht 1982: 130), although his influence was exercised mostly through the students he trained. During the first part of the century, the earliest English language monograph on obesity and 34 doctoral dissertations dealing with the subject were published. A common theme was the imbalance of various systems resulting in disease. For example, the essay by Thomas Short (1690-1772)—a pioneer in vital statistics—on the origin of corpulence attributed it to blood stored in the oily parts of the body and not sufficiently discharged by perspiration. Short thought that fat was stored in little bags. He noted that corpulence was more common in countries with “wet air,” which he believed decreased perspiration. Foods that were soft, smooth, sweet, and oily, as well as slothfulness, led to obesity. Thus, exercise was viewed as important, as were diets light in foods of a “detergent kind.” Less nutritious kinds of food, such as fish, were to be consumed sparingly. Also recommended was less sleep, a reduction in passions, gentle evacuations, and tobacco smoking to stimulate the nerves of the mouth (Bray 1992).

During the second half of the eighteenth century, Boerhaave’s students dispersed from Leyden to found new centers of clinical medicine at Edinburgh and Vienna, and during these years obesity, corpulence, and polysarcia became “species” following a Linnaean system of classification.

In the aftermath of the French Revolution, a new vitality emerged in clinical medicine, stimulated by the Paris Clinical School, as well as in basic sciences. The concept of energy balance developed, following the work of Antoine L. Lavoisier (1743-94) and the elaboration of the law of thermodynamics by Hermann L. F. von Helmholtz (1821-94). T. K. Chambers wrote extensively on obesity using theoretical models derived from thermodynamics.

English clinical medicine in the nineteenth century is notable for a work by W. Wardd entitled Comments on Corpulency, Liniments and Leanness (1829), which describes a number of clinical cases of massively obese individuals. In 1863 William Banting (1779-1878) penned the first popular diet pamphlet. Banting, a London undertaker, who had personally lost considerable weight to regain his health, advocated a diet of lean meat, dry toast, soft-boiled eggs, green vegetables, and liquids (Bray 1992).

The adipocyte (fat cell) was identified in German laboratories, and advances in neurology led to the description of several hypothalamic-pituitary causes of obesity, such as the Fröhlich syndrome (1901) and the Prader-Willi hyperphagia syndrome (1956); the Pickwickian hypoventilation syndrome (1956) is a nonneurologic type of obesity-associated ailment (Burwell et al. 1956; Butler 1990).

In the twentieth century we have seen an ever-growing understanding of the psychological, social, and neurophysiological mechanisms that control food intake.We have also just begun to develop important pharmaceutical interventions targeted at pathologies within these mechanisms.

Obesity in America

Hillel Schwartz (1986) and Jo Anne Cassell (1995) have both reviewed the history of obesity in the United States. Although many Americans currently associate body weight and size with moral weakness, such negative perspectives do not have a long history, and in fact, attitudes toward overweight people have changed many times throughout history. In general, when food was scarce, such individuals were viewed as prosperous and envied by their neighbors. By contrast, in times and societies with ample food, fashion usually favored slim and lean figures. In many instances, however, no moral judgments were attached to either overweight or lean status.

Beginning in the medieval period and continuing in America throughout the eighteenth century, morality plays were popular entertainment. Gluttony, one of the cardinal sins, frequently appeared as a theme involving excess or greed—and certainly a lack of self-restraint with regard to food and drink. The sin, however, was in consuming more than one needed and leaving others with less than their share. Body size or shape were not factors in gluttony, and being overweight carried no implication of sin.

In the early part of the nineteenth century, medicine focused on appetite and not thinness, and most physicians believed that fat represented a reserve that could be called upon in the event of disease, trauma, or emergency. Beginning at about mid-century, however, attitudes began to change under the influence of such individuals as Sylvester Graham (1794-1851) and the Kellogg brothers, who advocated a vegetarian regimen, coarsely milled flour, the consumption of cereal grains, and moderation in diet. They declared gluttony an evil, and obesity became a moral issue. During the Victorian period, however, in a counter-movement, fashion again began favoring a rounded body shape and seven-course family dinners. Diamond Jim Brady and his companion, Lillian Russell, were widely admired for their insatiable appetites and came to symbolize the exuberant excesses of the era (Cassell 1995).

By the turn of the twentieth century, scientists had come to believe that body fat had its origin in the fat of foods consumed and that dietary fat passed unchanged through the digestive tract to be absorbed and deposited. Fat was again out of fashion. Cartoons and jokes about overweight persons began to appear in newspapers and magazines. Stout, once a perfectly good word, became uncomplimentary, and a person who was fat was considered ugly. William Howard Taft, at 6 feet 2 inches tall, weighed 355 pounds when he was President of the United States (1909-13). Newspaper cartoons showed his rotund size, and when he got stuck in the White House bathtub, the event was well publicized. A variety of products to help in weight loss suddenly became available, including appetite suppressants, diuretics, stimulants, and purgatives. Special teas, bath salts, and mechanical devices were also employed (Schwartz 1986).

A 1912 study by actuaries of insurance policy holders provided height, weight, and mortality figures that became the data base for actuarial tables used to determine, for the first time, that there was a relationship between body weight, health, and mortality. According to these statistics, moderate weight gain was appropriate before age 35 but became increasingly harmful in later life. Excess body fat had become a serious health liability, and during World War I, the entire nation went on a diet. Rationing and conservation efforts designed to ensure adequate rations for the soldiers also conveyed the notion that it was patriotic to be thin; to carry excess weight was un-American.

Obesity researchers in the 1920s and 1930s were divided as to whether obesity was due to exogenous or endogenous causes. “Exogenous” people overate but had firm muscles and were basically in good health. They were cheerful and happy. “Endogenous” people had a deficient metabolism, flaccid muscles, and poor health and were sad or sour in nature. Not surprisingly, men were generally placed in the former group and women in the latter. For some researchers, weight was a genetic matter, with fatness a dominant trait and slenderness a recessive trait.

As early as 1911, thyroid supplements had become available and were regularly prescribed for “glandular” disorders. Indeed, for a brief period in the postwar years, American physicians thought that many obese patients were suffering from inadequate amounts of thyroid hormones. So long as it seemed that there were endocrinologic and genetic causes for obesity, there was once again an abatement of moral judgment. But in the 1930s, medicine concluded that few people had true thyroid deficiencies after all, and nutritional scientists had reached the position that people were overweight simply because they ate too much. Moral judgments returned, and obesity was recast as the outcome of psychological problems leading to overeating.

The introduction of motion pictures with their frequently svelte movie stars led, among other things, to the popularity of weight-loss diets, particularly those originating in California. Perhaps the most famous was the “Hollywood 18-Day Diet.” Another was the “banana diet”—the product of bananas and skim milk in a blender—and a forerunner of today’s liquid diets.

Research emphasis changed once again in the 1940s as scientists defined obesity as “over-fatness.” People learned that they might be overweight, but not overfat, and dieticians began to measure body fat with skinfold calipers. Psychological theories focused on such issues as depression, lack of self-esteem, boredom, and inner emptiness as precursors to overeating, which also acted as popular explanations. Fatness as a signal of psychological distress continues to be influential in many weight-loss programs that employ support groups.

In the 1950s, changes in American society brought more attitudinal changes about dieting and weight control. Supermarkets began to offer a number of low-calorie and diet products. Among these were 900-kilocalorie-per-day liquid-diet formulas that were an instant success and continue to be widely available in the United States. Surveys reported that 40 percent of all families were regularly using low-calorie or diet products by 1962 and 70 percent by 1970 (Cassell 1995).

In today’s marketplace, novel fat substitutes are occupying shelves along with earlier sugar substitutes. New products from cookies to ice cream are both fat and sugar free. Books on dieting have also been popular, and in the 1960s, those on weight loss were best-sellers, especially if the authors promised that loss without the need to give up one’s favorite foods. Five million copies of The Doctor’s Quick Weight Loss Diet (Stillman and Baker 1967) were sold in 1967 alone, and books on dieting continued to lead book sales in the 1990s. In addition, in 1972 psychological therapy started to employ behavioral therapy, which has continued as a popular approach both for diet groups and commercial weight-loss centers. How, why, and where persons ate became as important as what they ate.

In the 1980s,Americans began to focus on physical fitness and exercise as a way to promote good health. A plethora of articles on dieting appeared in newspapers and popular magazines, along with information on increased activity levels. The message was to lose weight with exercise and diet, so as to be happier, healthier, and more attractive. A diet industry mushroomed to assist Americans in losing weight.The number trying to do so was estimated to be one-fourth of men and one-half of women, and annual sales of diet products had exceeded 30 billion dollars by the end of the 1980s.

Nonetheless, the incidence of obesity in America continued to increase and, predictably, there has been something of a backlash. In today’s environment some overweight individuals have used the courts to press cases of discrimination based on body size, and there is a growing antidiet movement, with fashion houses, magazines, and psychological and educational support groups that champion the obese. These groups, such as the National Association to Advance Fat Acceptance (California), Ample Opportunity (Oregon), and the Diet/Weight Liberation Project (New York), promote positive images of obese individuals, arrange for social gatherings with singles groups, and work toward equity at places of employment and other venues where there is discrimination against obese individuals.

Many groups have newsletters; there are a number of national magazines, such as Radiance: The Magazine for Large Women (Oakland, Calif.), and some presses specialize in publications about obesity, food, eating disorders, and related psychosocial, political, and medical issues, as, for example, Fat Liberation Publications (Cambridge, Mass.). Other inroads are being made in the media and on educational and economic fronts to reduce the stigma of obesity in the United States. Given the high percentage of over-weight Americans, the tide may once again be turning.

Nonetheless, Cassell (1995) suggests that weight watching and concern for body image have become an integral part of American culture as we enter the twenty-first century, and there is still great pressure to be thin.The health risks of excessive body fat are well documented scientifically, and articles on the subject appear daily in the popular literature. At the same time, a person’s overweight status does not automatically imply ill health, and more effort on the part of health professionals is being directed toward evaluating an individual’s overall health status before a recommendation for weight loss is made.

Causes of Obesity

Obesity has a multifactorial etiology, which includes genetic factors, metabolic and behavioral phenotypes, and environmental agents. Because it is a condition of excessive storage of energy, an understanding of energy balance is fundamental to understanding obesity. Energy balance is equal to energy intake minus energy expenditure, and, consequently, obesity becomes the result of a positive energy balance. Yet, energy balance is exquisitely sensitive. The average nonobese American male consumes approximately 1 million kilocalories per year, but his body fat stores remain unchanged if he expends an equal number of calories. However, a change of only 10 percent either in intake or output can lead to a 30-pound weight change in a single year (Bray 1987). More subtly, a gain of 11 kilograms (24 pounds) of weight during a 40-year time span can come about with a mean daily discrepancy between intake and expenditure of only 5 kilocalories.

Energy Intake

Individual differences in metabolic mechanisms are not well understood. Cross-sectional studies reporting energy intake for individuals with different body compositions have found that obese individuals may have high, normal, or even low energy intakes relative to normal-weight subjects (Lachance 1994) and that there is a poor correlation between daily energy intakes and expenditures (Edholm 1973). For most adults, the sensitivity of the energy balance system for change is less than 1 percent per year. The “normal” adult contains 140,000 kilocalories of energy in body fat, 24,000 kilocalories in protein, and only about 800 kilocalories in carbohydrate. Consequently, although an individual consuming 2,000 kilocalories per day of which 40 percent is carbohydrate will ingest an amount of carbohydrate comparable to body stores, protein intake will average only about 1 percent of total stores and fat intake considerably less than 1 percent (Bray 1987, 1993a, 1993b).

Energy balance with regard to the macronutrients has been illuminated in recent years by the discovery of specific enzymes and neurotransmitters with receptors in the central nervous system. The brain is sensitive to changes in circulating glucose levels, and a glucostatic mechanism may regulate the intake of fat and carbohydrates—the primary energy substrates. Carbohydrate stores have a high turnover rate and can be depleted quickly and frequently so that signals exist to monitor and correct for carbohydrate imbalances. Fat stores, on the other hand, are nearly limitless, and turnover is slow and infrequent. Thus, as a rule, increased energy intake results in increased fatness (Bray 1993a; Horton et al. 1995).

Energy Expenditure

Energy expenditure has a number of components, the most important of which is basal metabolic rate (BMR). The total energy cost of any given activity is equal to the BMR plus the work done and the heat produced. For sedentary populations, the BMR may comprise 50 percent to 70 percent of the daily energy expenditure. Wide variations in BMR are not accounted for by food intake, meaning that those people with the highest calculated BMRs are not those who eat the most food. However, BMR is depressed in starvation, in individuals with a restricted caloric intake, and in many obese individuals (Bouchard 1994).

Consistent with these findings are studies of energy expenditure involving both involuntary (for example, fidgeting) and voluntary movement that indicate that physical activity is reduced in obese individuals. However, even though physical activity is reduced, there is a higher cost for activity in over-weight individuals, resulting in a tendency toward normal or even high levels of energy expenditure for a particular physical activity. In these instances much of the energy is lost as heat, rather than in muscular work. One problem of cross-sectional data is that finding an average level of energy intake for an individual who is already obese tells us little about previous levels of energy intake and energy expenditure that may have contributed to the development of obesity in the first place.

It is likely that genetic predisposition to obesity lies not only in a lower BMR but also in the reduction of heat production that occurs following a meal, that is, in lower diet-induced thermogenesis. A subnormal thermogenic response to food has been reported in clinical experiments among obese individuals and those who have been obese in the past (the post-obese), as well as among subjects maintaining a desirable weight on relatively low food intake. In sum, obese individuals are metabolically more efficient than lean individuals.

Taste Preference and Obesity

Taste preferences represent a major determinant of food intake and have been linked to obesity and weight gain. Genetic differences in taste preferences are heritable (Perusse and Bouchard 1994). For example, sensitivity to phenylthiocarbamide (PTC) is controlled by a major single gene. Individuals who can taste PTC, a bitter synthetic compound, avoid or reduce intake of foods containing chemically similar, but naturally occurring, compounds, such as cabbage, broccoli, and Brussels sprouts. Research indicates that some obese individuals may have an elevated preference for foods high in carbohydrates and fats, such as ice cream, chocolate, or pastries (Drewnowski 1988). In contrast, anorectic subjects show a preference for sweet but not for fatty foods. Food preferences may be regulated, in part, by peptides that stimulate the central nervous system, increasing neurotransmitters, such as beta endorphins, and, consequently, feelings of well-being. Finally, simply tasting (not swallowing) fat, either in cream cheese or peanut butter, increases insulin production and serum triglycerides. Such findings suggest that sensory receptors in the mouth initiate digestive responses not triggered directly by the nutrient and that the sensory qualities of fat may promote preference for fatty foods (Radloff 1996).

Psychological Factors

In recent years there has been a major change in discussions concerning the psychological aspects of obesity. In earlier psychogenic theories, obese persons were assumed to suffer from emotional disturbances and failures of impulse control. However, systematic assessment of the nature and extent of psychological problems of obese individuals have changed the psychogenic views of obesity to a somatogenic one. The psychosocial problems in question arise primarily from the stigma attached to obesity in contemporary societies.

Genetic Factors

Investigations of the genetic factors in human obesity have developed rapidly. Traditional family studies of parent, offspring, and sibling data identify the extent to which obesity is familial, but they pose the problem of separating the shared environment of families from genetic factors. Adoption studies overcome some of the difficulties encountered in family studies because individuals have a shared environment but not a biological relationship. Moreover, identical and fraternal twin studies can shed light on genetic as well as environmental contributions (Bouchard et al. 1988, 1990; Bouchard 1994).

Inheritable features include metabolic rates, hormone andenzyme levels, and the amount and patterning of subcutaneous fat. Data from a number of studies indicate that Body Mass Index has a heritability (range 0 to 1) from 0.4 to 0.6, suggesting that genes may be responsible for approximately one-half of the total phenotypic variation in obesity. Adoption studies found that BMIs correlated more strongly with biological than adoptive parents. Investigations in Denmark and Iowa of adult twins showed a high heritability of 0.8. Additive and nonadditive genetic components point to many obesity-promoting genes (Bouchard 1994).

A number of important genes that control eating and weight gain have been discovered in mice. These have human analogs, but obesity-promoting mutations of these genes have not been located in humans. Recently, mutations in the leptin receptor gene have been found among the Pimas of Arizona, the Finns, and the French (Bouchard and Bray 1996; Gibbs 1996).The obese gene encodes for leptin, a hormone produced by fat cells. Mice with a mutation in this gene produce either no leptin or a malformed version and are obese with weights up to three times those of normal mice. The diabetes gene codes for a receptor protein that responds to leptin by reducing appetite and increasing metabolism. Mice with a mutation of this gene do not receive the leptin signal and get very fat from infancy. Other genes are “fat” and “tubby.” Mice with mutations in either gene put on weight gradually, more like the human pattern. Recent work on leptin and leptin receptors has focused on developing appropriate pharmacological interventions. Leptin causes obese and normal mice to lose weight by signaling the brain that the body has enough fat,which in turn suppresses appetite.

The search for genes and their products that control appetite led to the discovery in 1996 of the hormone urocortin, which is a powerful appetite suppressant in rats. Other promising research has concentrated on a neuropeptide that stimulates appetite and on lipoprotein lipase, an enzyme involved in fat deposition (Gibbs 1996).

Consequences of Obesity

Mortality

A number of studies have focused on mortality and morbidity associated with overweight and obesity. Those done in Norway, Canada, and the United States indicate that BMIs associated with lowest mortality lie in the range of 15 percent below to 5 percent above ideal weight, although recently, some physicians have argued that failure to control for the effects of smoking produces an artificially high mortality in leaner subjects. All studies with more than 20,000 participants have shown a positive relationship between overweight and mortality. But the Build Study of 1979 indicated that above-average weights are associated with optimal life expectancy. Moreover, 40 percent of all smaller employee, community, and random population studies have failed to demonstrate a relationship between body weight and mortality (Sjostrom 1993).

Similarly, the First National Health and Nutrition Examination Survey 9-year follow-up found that there was no additional risk associated with overweight among women and a statistically significant but moderate additional risk (relative risk 1.1 to 1.2) for men ages 55 to 74 years. Low body weight, however, was associated with increased mortality (relative risk 1.3 to 1.6), except for women age 55 to 64 years. These results suggest a need for clinically specific definitions of obesity and overweight, especially among the elderly (Tayback, Kumanyika, and Chee 1990).

A change in weight has also been associated with mortality in adulthood. The Nurses’ Study, using age 18 as the standard, showed that increases in weight up to 9.9 kg either reduced or left unchanged the relative risk of mortality. However, weight increases of 10 to 19.9 kg and 20 to 34.9 kg resulted in relative risks of 1.7 and 2.5, respectively. In the Framingham Study, an estimated 10 percent loss in body weight corresponded with a 20 percent reduction in the risk of developing coronary artery disease (Committee on Diet and Health 1989). Independent of weight or BMI, a high waist-to-hip ratio or large deposits of fat in the center of the body (related to internal stores of visceral fat) are associated with increases in mortality and morbidity.

Data also suggest that obesity as assessed by BMI or other measures may mean different mortality and morbidity risks for different populations. For example, overall mortality was not associated with obesity among the Pima except for the most obese men (Knowler et al. 1991).Among Japanese-American men in the Honolulu Heart Program, the BMI, subscapular skinfold thickness and central obesity predicted coronary artery disease, but only subscapular skinfold thickness predicted stroke (Curb and Marcus 1991b).

Morbidity

A wide variety of disorders and problems are caused or exacerbated by obesity (National Institutes of Health 1985; Bouchard and Johnston 1988), and T. Van Itallie (1985) has listed these by organ system. For the cardiovascular system they are premature coronary artery disease, ventricular arrhythmia and congestive heart failure, hypertension, stroke, and varicose veins. Obesity can affect the respiratory system in terms of alveolar hypoventilation or the Pickwickian syndrome, obstructive sleep apnea, and ventricular hypertrophy. Under the digestive system rubric there may be an increase in gall bladder and liver diseases. For the hormonal and metabolic systems, diabetes mellitus, gout, and hyperlipidemia are the most common results of obesity. Kidneys may be affected, resulting in proteinuria and renal vein thrombosis. The skin may develop striae and plantar callus, and osteoarthritis of the knee and spine are exacerbated by obesity. Obesity increases the risk of endometriosis and breast cancer in women and can impair reproductive and sexual functions. Obesity also enhances the risk of surgical and anesthetic procedures and reduces physical agility, which can lead to accident proneness. Finally, obesity may interfere with the diagnosis of other disorders by physically obscuring their presence.

Social Stigma of Obesity

Obese individuals in the United States suffer from social and psychological prejudice. Even children hold these prejudices. When a group of 6-year-olds were shown a fat person’s silhouette and asked to describe the person’s characteristics, they said “lazy, cheating and lying” (Czajka-Narins and Parham 1990). In another study where children were shown drawings of an obese child, a child in a wheelchair, a child on crutches, a facially disfigured child, and a child amputee, they disliked only the latter more than the overweight child. Furthermore, children prefer to play with thin rather than fat rag dolls, and parents prefer to have thin rather than obese children photographed.

Obese adolescent females have reported fewer dates and less participation in school organizations than nonobese adolescents. College students, when asked whom they were least likely to marry, ranked obese individuals fifth lowest in desirability, following an embezzler, a cocaine user, an ex-mental patient, and a shoplifter. Adults rate nonobese figures as happier, having more friends, smarter, more attractive, less lonely, and less mean than obese persons. College students in another study stated that obese individuals were warm and friendly but also unhappy, without self-confidence, self-indulgent, undisciplined, lazy, and unattractive. It is interesting, however, that psychological profiles of obese individuals show personality characteristics and achievement levels that belie these prejudicial views (Probart and Lieberman 1992).

Health professionals in the United States also hold negative views of obese individuals. They consider obese individuals to be hypochondriacal, possessing impaired judgment, having inadequate hygiene, and indulging in inappropriate and self-injurious behavior. Additionally, they find obesity to be aesthetically displeasing. As mentioned, there is an active segment of the U.S. population working to counter such widespread prejudices (Price et al. 1987).

Treatment for Obesity

Dieting

Dieting is a routine aspect of life for many Americans, even among some who are not obese. Studies indicate that in the United States, 33 to 44 percent of adult women and 22 to 34 percent of adult men are actively dieting at any given time and that Americans spend an estimated 30 to 50 billion dollars a year on weight-loss programs. The incidence of dieting varies little by ethnicity for women, but among men, Hispanic Americans have the highest proportion of dieting and African-Americans the lowest. Dieting is most common among well-educated and higher socioeconomic classes (Kopelman et al. 1994; Elmer-Dewitt 1995).

Reports of dieting by high-school-age students are common. The National Adolescent Student Health Survey of eighth and tenth graders revealed that 61 percent of girls and 28 percent of boys reported dieting to lose weight. However, a longitudinal study of Arizona adolescents by the Nichters (1991) found extensive discourse about dieting but little modification of food behaviors or weight loss. Very few girls in this study reported using vomiting, diet pills, laxatives, or diuretics as weight-control methods. Many girls responded that they did not “diet to lose weight” but rather “watched what they ate continually” and avoided “fattening foods.” Eighty-five percent rarely or never counted calories, nor did they know how many calories they consumed.

Although caloric restriction (usually 1,200 to 1,000 kcal/day) should be the only method of treatment for obesity, long-term analyses of results show that 95 percent of those who are successful at weight loss regain it within one to two years. Very low calorie diets (400 to 800 kcal/day) lead to rapid weight loss, but there is little evidence that long-term weight maintenance is improved. Repeated weight gain and loss cycles are called weight cycling or yo-yo dieting. Although there are questions about altered metabolism with weight cycling, lean tissue mass does not appear to be lost at an increased rate with each cycle (Garner and Wooley 1991).

Many weight-loss programs provide special foods low in calories and high in fiber as part of a comprehensive program. Weight-reduction clinics and lay support groups use a combination of diet with behavioral and exercise intervention. These approaches have costs associated with them, ranging from expensive diet clinics that provide specialized care with a multi-disciplinary team of psychologists, dieticians, physicians, and exercise specialists to inexpensive lay support groups, such as Weight Watchers, Take Off Pounds Sensibly (TOPS), and Overeaters Anonymous. Recently, work-site and school weight-control groups have also been formed, emphasizing both weight loss and relapse prevention.

Behavioral therapy as an adjunct to dietary treatment improves compliance and may improve long-term results. Elements of behavioral therapy include self-monitoring of dietary intake; control of external eating stimuli; analyses and changes in eating behavior, including speed, time of day, and locus of activity; rewards for weight loss and weight maintenance; nutritional education; physical activity to improve both weight loss and overall well-being; and cognitive restructuring, concentrating on positive goals to counter negative, self-defeating thoughts (Kanarek et al. 1984).

Exercise

A number of mechanisms have been proposed to explain the association between exercise and weight control. The most frequently advanced benefits are an increase in lean body mass, resulting in a higher basal metabolic rate; increases in metabolic rate produced by the exercise and enduring beyond specific bouts of exercise; the energy expenditure of the activity itself; and the psychological benefits, including self-esteem, modulation of mood, and improved body image. The current recommendation is for regular low-level exercises (a heart rate below 60 or 70 percent of the maximum) that are beneficial and easy to maintain over a long duration.

A number of techniques can be employed to improve adherence to an exercise plan. These include setting goals, a program of relapse prevention, and behavior changes involving stimulus control and reinforcement in a social environment, perhaps including one’s spouse. When they begin to exercise, many over-weight individuals face a combination of physical and psychosocial burdens related to negative feelings associated with past experience. Some studies indicate that exercise alone can produce a modest gain in lean body mass and a loss in fat in weight-stable individuals. However, both animal and human experiments show that exercise does not conserve lean weight in the face of significant energy deficit (Stunkard and Wadden 1992; Bouchard and Bray 1996).

Drugs

In cases of extreme obesity or when there is fear of comorbidities associated with a central distribution of fat, drug therapy may be warranted. These drugs include agents that act on the noradrenergic and serotonergic systems, opioid receptors, and peptide agonists or antagonists. The most popular drugs—fenfluramine, fluoxetine, or dexfenfluramine and phentermine—increase serotonin levels. Other classes of drugs include thermogenic drugs, growth hormone agonists, and drugs that act directly on the gastrointestinal system, including enzyme inhibitors and inhibitors of absorption. These drugs are not without risk (heart valve abnormalities and pulmonary hypertension, for example, have been linked to a phentermine-fenfluramine pill) and, in fact, have not been used with substantially large populations long enough to assess long-term benefits or risks. This is partly because there was a hiatus of about 20 years in the United States when drugs were not developed specifically to treat obesity. Now, however, there are a number of pharmaceutical companies in the process of developing such new drugs (Gibbs 1996).

Surgery

A surgical procedure may be warranted for morbidly obese individuals. This may be in the form of liposuction or surgical reduction of fat deposits, usually from the abdominal apron. But food ingestion can be restricted by temporarily wiring the jaws, or its absorption can be reduced either through the reduction of stomach capacity by stapling or by creating a small intestinal bypass. Surgical intervention, however, is not without risk and sequelae, such as severe diarrhea.

Summary

Overweight and overfatness (that is, obesity) are conditions of epidemic proportions related to food consumption and activity patterns. The human ability to store fat and selectively mobilize it evolved as a defense against food shortages, cold climates, demanding physical labor, disease, and the physiological requirements of pregnancy and lactation. Our understanding of the physiological and genetic basis for obesity has increased considerably in the last decade.

Obesity has been linked to increased mortality and morbidity in nearly all organ systems. Moreover, psychosocial stigmatizing of the obese, at least in affluent countries, has an adverse impact on their education, occupation, social interaction, and self-esteem.

In the United States, a mult-ibillion-dollar “diet industry” has developed that includes new diet products, medications, clinics, health clubs, support groups, and obesity specialists. With all of these efforts, including the increasing availability of fat- and sugar-free foods, we continue to get fatter—in the United States and around the world.